The present invention relates to a multiple pack for substantially bowl-shaped, thin-walled, disposable vessels having a relatively stiff upper peripheral collar, and to methods and means for manufacturing such multiple packs.
The invention is of particular utility in the folding of thin-walled vessels of disposable type which, when stacked in the normal way, or individually, take up considerable space. For purposes of illustration, the invention will be described herein with reference to disposable inserts used as cooking vessels, although it is not in any way limited to such use.
Bowl-shaped, thin-walled, disposable inserts used with cooking vessels are known, and are described, for example, in U.S. Pat. No. 4,164,174. They are manufactured from a thin, flexible material capable of good heat transfer from a thermally conducting medium such as water vapor to the food contained therein. The insert is intended to be placed in a special support such as a mesh basket or the like, which, in turn, is placed inside a cooking vessel of conventional design. To facilitate its placement in the basket, such an insert is usually provided with a stiff upper edge or collar, the remainder of the wall and bottom portions being thin walled. The insert may be vacuum molded of a polythene material and formed so that the wall thickness of the upper portion or stiff upper collar is about 0.1 mm and the wall thickness of the sides and bottom is about 0.01-0.03 mm.
Since the inserts are disposable, and are therefore quickly used up, it is desirable for distribution purposes to market them in packs of convenient size, say 10-100 inserts stacked one inside the other in a suitable envelope or protective casing. However, since a typical insert may have a volume capacity of two liters, a diameter of roughly 200 mm and a height of about 180 mm, such inserts tend to be rather bulky from the standpoint of shipping, storage and handling, even when stacked. Also, since the sides and bottoms of such inserts are extremely flexible, it is sometimes difficult to stack them together.